In your own words, explain how Earth's magnetic field is created and how it benefits human life.

Well they want you to describe it in your own words, so I'm not going to write your essay/explanation for you.
What level physics is this? Are you familiar with the fact that an electric current produces a magnetic field?

Circulating electric current in earth's metallic core produces magnetic field due to earth's rotation. This magnetic field helps to remove high energy charged particles from entering earth's atmosphere and thus protects living things from harmful effects of radiation.